Coating process method and coating process apparatus

ABSTRACT

A coating process method in which a coating liquid is discharged onto the surface of a target substrate to be processed while rotating the target substrate so as to expand the coating liquid radially outward on the target substrate and, thus, to form a coated film comprises the step of detecting that the actual discharging of a coating liquid from a coating liquid discharging nozzle is started, and the step of controlling based on a signal of the detection at least one of the driving timing of a pump for allowing the coating liquid to be discharged from the coating liquid discharging nozzle, the operation timing of a valve mounted to a pipe for supplying the coating liquid into the coating liquid discharging nozzle, and the rotation starting or stopping timing of the target substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a coating process method and acoating process apparatus, in which a substrate such as a semiconductorwafer is coated with a liquid coating material such as a resist.

[0003] 2. Description of the Related Art

[0004] In the manufacturing process of a semiconductor device, a resistpattern that is used as a mask for forming a prescribed pattern isformed by means of a so-called “photolithography technology”, in which aresist solution is supplied onto a semiconductor wafer so as to form aresist film, followed by applying a light exposure treatment in aprescribed pattern to the wafer after the resist coating step andsubsequently developing the light-exposed pattern formed on the resistfilm on the wafer. In the resist coating process among the manufacturingsteps noted above, a spin coating method is employed in many cases as amethod for uniformly coating the wafer surface with the resist solution.

[0005] In the spin coating method, a resist solution is dripped from aresist nozzle arranged above the wafer W onto the central portion of thewafer surface while rotating the wafer W together with a spin chuck by arotary driving mechanism, with the wafer W held stationary on the spinchuck by means of vacuum suction. The dripped resist solution iscentrifugally expanded radially outward on the wafer surface so as toform a resist film on the entire surface of the wafer W. Then, thedripping of the resist solution is stopped, and the rotation of thewafer W is continued so as centrifugally remove the extra resistsolution on the wafer surface, thereby controlling the thickness of theresist film and drying the resist film.

[0006] In order to form a resist pattern with a high precision, it isnecessary to form the resist film in a prescribed uniform thickness overthe entire surface of the wafer W. Also, for forming the resist film ina uniform thickness over the entire surface of the wafer W, it isimportant to control strictly the resist solution dripping time, and thetiming of the resist solution dripping and the wafer rotation inaddition to the rotating speed and the rotating time of the wafer W.

[0007] It was customary in the past to supervise the thickness and thethickness distribution of the resist film by controlling the coatingdevice, etc. with a software.

[0008] However, in the conventional resist solution supply mechanism,resist discharging nozzles of a plurality of resist coating processunits are connected to a single resist solution discharging pump, withthe result that, because of the installing conditions such as thedifference in head, the discharging timing of the resist solution tendsto be rendered nonuniform depending on the resist solution dischargingnozzle used even if the resist solution is discharged on the basis ofthe same recipe. The discharging timing of the resist solution is alsorendered nonuniform by the individual variation of the air operationvalve used as an opening-closing valve of the resist solution supplypipe or the resist solution discharging pump. Such a nonuniformity inthe discharging time was not handled as a serious problem in the past.However, a prominent progress is being achieved in recent years in theminiaturization of the semiconductor device and in the enlargement inthe diameter of the semiconductor substrate to be process. In thisconnection, very high levels of the demands for the accuracy in thethickness of the resist film and for the uniformity of the resist filmthickness are being raised nowadays. It follows that even thenonuniformity in the discharging timing of the resist solution caused bythe difference in head and by the individual variation has come toaffect seriously the thickness and the uniformity of the thickness ofthe resist film. It should also be noted that the reduction in thedischarging amount of the resist solution (resist saving) is beingpromoted in recent years so as to affect the change in the dischargingamount and the change in the discharging rate of the resist solution.

BRIEF SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a coatingprocess method and a coating process apparatus, which permit forming acoated film such as a resist film with a high accuracy and a highuniformity in the film thickness.

[0010] According to a first aspect of the present invention, there isprovided a coating process method in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising the steps of detecting that the actual discharging of acoating liquid from a coating liquid discharging nozzle is startedand/or stopped; and controlling the coating treatment on the basis of asignal of the detection.

[0011] According to a second aspect of the present invention, there isprovided a coating process method in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising the steps of detecting that the actual discharging of acoating liquid from a coating liquid discharging nozzle is started; andcontrolling based on a signal of the detection at least one of the drivetiming of a pump for allowing the coating liquid to be discharged fromthe coating liquid discharging nozzle, the operation timing of a valvemounted to a pipe for supplying the coating liquid into the coatingliquid discharging nozzle, and the rotation starting or stopping timingof the target substrate.

[0012] According to a third aspect of the present invention, there isprovided a coating process method in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising the steps of detecting that the actual discharging of acoating liquid from a coating liquid discharging nozzle is stopped; andcontrolling based on a signal of detection at least one of the drivestop timing of a pump for allowing the coating liquid to be dischargedfrom the coating liquid discharging nozzle, the operation timing of avalve mounted to a pipe for supplying the coating liquid into thecoating liquid discharging nozzle, and the rotation stop timing of thetarget substrate.

[0013] According to a fourth aspect of the present invention, there isprovided a coating process apparatus in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising a substrate holding member for holding substantiallyhorizontal a target substrate to be processed; a motor for rotating thesubstrate holding member; a coating liquid discharging nozzle fordischarging a coating liquid onto the target substrate held by thesubstrate holding member; a pump for allowing the coating liquid to bedischarged from the coating liquid discharging nozzle; a valve mountedto a pipe for supplying the coating liquid into the coating liquiddischarging nozzle; a detecting device optically detecting that thedischarging of the coating liquid from the coating liquid dischargingnozzle has been started; and a controller receiving a signal of thedetection from the detecting device so as to control based on thedetection signal at least one of the drive timing of the pump forallowing the coating liquid to be discharged from the coating liquiddischarging nozzle, the operation timing of the valve, and the drivestarting or stopping timing of the motor.

[0014] According to a fifth aspect of the present invention, there isprovided a coating process apparatus in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising a substrate holding member for holding substantiallyhorizontal a target substrate to be processed; a motor for rotating thesubstrate holding member; a coating liquid discharging nozzle fordischarging a coating liquid onto the target substrate held by thesubstrate holding member; a pump for allowing the coating liquid to bedischarged from the coating liquid discharging nozzle; a valve mountedto a pipe for supplying the coating liquid into the coating liquiddischarging nozzle; a detecting device for optically detecting that thedischarging of the coating liquid from the coating liquid dischargingnozzle has been finished; and a controller receiving a signal of thedetection from the detecting device so as to control based on thedetected signal at least one of the drive stop timing of the pump forallowing the coating liquid to cease to be discharged from the coatingliquid discharging nozzle, the operation timing of the valve, and thestop timing of the motor.

[0015] According to the first aspect of the present invention, a signaldenoting that the discharging of the coating liquid from the coatingliquid discharging nozzle has been actually started and/or stopped isdetected, and the coating treatment is controlled on the basis of thedetected signal. It follows it is possible to control the variousconditions on the basis that the time when the coating liquid has beenactually discharged is grasped so as to make it possible to form acoated film such as a resist film with a high accuracy in the filmthickness and with a high uniformity in the film thickness.

[0016] To be more specific, in the conventional control based on asoftware, an “open” signal, i.e., a signal to open the valve, is simplytransmitted to the valve mounted to the nozzle in allowing a coatingliquid such as a resist solution to be discharged. However, the timebetween the actual transmission of the “open” signal to the valve andthe actual discharging of the resist solution tends to be renderednonuniform by the difference in the head of the resist solution supplynozzle and by the individual variation of the pump or the valve, withthe result that it is possible for the actual discharging of the coatingliquid to be deviated from the predetermined discharging timing of thecoating liquid. Under the circumstances, the discharging timing of thecoating liquid is controlled with a high accuracy in the presentinvention by detecting the actual starting and/or stopping in thedischarging of the coating liquid so as to make it possible to form acoated film with a high accuracy in the film thickness and with a highuniformity in the thickness of the coated film.

[0017] To be more specific, as in the second and fourth aspects of thepresent invention referred to above, a signal denoting that thedischarging of the coating liquid from the coating film dischargingnozzle has been actually started is detected in the present invention,and at least one of the drive timing of the pump for allowing thecoating liquid to be discharged from the coating liquid dischargingnozzle, the operation timing of the valve mounted to the pipe forsupplying the coating liquid to the coating nozzle discharging nozzle,and the rotation starting or stopping timing of the target substrate tobe processed is controlled on the basis of the detected signal so as toprevent the inconveniences causing the fluctuation of the film thicknesssuch as the inconvenience that the rotating speed of the targetsubstrate to be processed is excessively high in the stage ofdischarging the coating liquid and the inconvenience that the actualdischarging time is short.

[0018] In this case, it is possible to obtain a delay time from thetiming for actually discharging the coating liquid on the basis of thedetected signal denoting that the discharging of the coating liquid hasbeen started and to control based on the delay time thus obtained atleast one of the drive timing of the pump for allowing the coatingliquid to be discharged from the coating liquid discharging nozzle, theoperation timing of the valve mounted to the pipe for supplying thecoating liquid into the coating liquid discharging nozzle, and therotation starting and/or stopping timing of the target object to beprocessed.

[0019] Also, as in the third and fifth aspects of the present inventionreferred to above, the actual discharging time of the coating liquid canbe controlled strictly in the present invention by detecting that thedischarging of the coating liquid from the coating liquid dischargingnozzle has been actually stopped and by controlling based on a signal ofthe detection at least one of the stop drive timing of the pump forallowing the coating liquid to be discharged from the coating liquiddischarging nozzle, the operation timing of the valve mounted to thepipe for supplying the coating liquid into the coating liquiddischarging nozzle, and the rotation stop timing of the target substrateto be processed, with the result that it is possible to further improvethe accuracy in the thickness of the coated film and the uniformity ofthe film thickness.

[0020] In this case, it is possible to detect a signal denoting that thedischarging of the coating liquid from the coating liquid dischargingnozzle has been actually started, to obtain based on the detected signala delay time from the timing at which the coating liquid should beactually discharged, and to control based on the delay time thusobtained at least one of the stop drive timing of the pump for allowingthe coating liquid to be discharged from the coating liquid dischargingnozzle, the operation timing of the valve mounted to the pipe forsupplying the coating liquid into the coating liquid supply nozzle, andthe rotation stop timing of the target substrate to be processed.

[0021] A signal denoting that the discharging of the coating liquid hasbeen started or stopped can be detected by an optical detecting device,e.g., an optical sensor. An optical sensor equipped with a fiber sensorfor projecting light and a fiber sensor for receiving light is easy tohandle and, thus, is adapted for use in the present invention. It isalso possible to use a CCD camera as the optical detecting device usedfor the detection. It is possible to detect that the discharging of thecoating liquid has been started or stopped in discharging the coatingliquid from the coating liquid discharging nozzle onto the targetsubstrate to be processed or when the coating liquid discharging nozzledischarges the coating liquid in a position retreated from the targetsubstrate to be processed.

[0022] According to a sixth aspect of the present invention, there isprovided a coating process method in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising the steps of actually detecting the state in startingand/or stopping the discharging of the coating liquid from a coatingliquid discharging nozzle; and controlling based on the data detected inthe detecting step the operating speed of a valve mounted to a pipe forsupplying the coating liquid into the coating liquid discharging nozzlein a manner to permit the state in starting and/or stopping thedischarging of the coating liquid to fall within an allowable range.

[0023] According to a seventh aspect of the present invention, there isprovided a coating process method in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising the steps of detecting that the coating liquid is beingactually discharged from the coating liquid discharging nozzle;measuring the actual discharging time during which the discharging ofthe coating liquid was detected in the detecting step; comparing theactual discharging time measured in the measuring step with the set timefor the discharging of the coating liquid; and judging that there is anabnormality in the case where the difference between the actualdischarging time and the set time is not smaller than an allowablevalue.

[0024] According to an eighth aspect of the present invention, there isprovided a coating process apparatus, comprising a substrate holdingmember for holding substantially horizontal a target substrate to beprocessed; a motor for rotating the substrate holding member; a coatingliquid discharging nozzle for discharging a coating liquid onto thetarget substrate held by the substrate holding member; a pump forallowing the coating liquid to be discharged from the coating liquiddischarging nozzle; a valve mounted to a pipe for supplying the coatingliquid into the coating liquid discharging nozzle; a detecting devicefor optically detecting the state in starting and/or stopping thedischarging of the coating liquid from the coating liquid dischargingnozzle; and a controller for controlling based on the data detected bythe detecting device the operating speed of the valve in a manner topermit the state in starting and/or stopping the discharging of thecoating liquid to fall within an allowable range.

[0025] Further, according to a ninth aspect of the present invention,there is provided a coating process apparatus, comprising a substrateholding member for holding substantially horizontal a target substrateto be processed; a motor for rotating the substrate holding member; acoating liquid discharging nozzle for discharging a coating liquid ontothe target substrate held by the substrate holding member; a pump forallowing the coating liquid to be discharged from the coating liquiddischarging nozzle; a valve mounted to a pipe for supplying the coatingliquid into the coating liquid discharging nozzle; a detecting devicefor optically detecting that the coating liquid is being actuallydischarged from the coating liquid discharging nozzle; a timer formeasuring the actual discharging time during which the discharging ofthe coating liquid is detected by the detecting device; a controller forcomparing the actual discharging time measured by the timer with the settime of the coating liquid discharging; and judging that there is anabnormality in the case where the difference between the actualdischarging time and the set time is not smaller than an allowablevalue.

[0026] According to the sixth and eighth aspects of the presentinvention, the state in starting and/or stopping the discharging of thecoating liquid from the coating liquid discharging nozzle is actuallydetected, and the operating speed of the valve mounted to the pipe forsupplying the coating liquid into the coating liquid discharging nozzleis controlled based on the detected data in a manner to permit the statein starting and/or stopping the discharging of the coating liquid tofall within an allowable range. It follows that it is possible to set inadvance the state of the coating liquid in the starting and/or stoppingtime of the discharging operation to fall within an allowable range soas to make it possible to avoid the detrimental effects given by thestate of the coating liquid in starting and/or stopping the dischargingoperation to the accuracy in the thickness of the coated film and to theuniformity of the film thickness.

[0027] Further, according to the seventh and ninth aspects of thepresent invention, it is detected that the coating liquid is beingactually discharged from the coating liquid discharging nozzle, thedetected actual discharging time is measured, and the measured actualdischarging time is compared with the set time of the discharging of thecoating liquid. Where the difference between the actual discharging timeand the set time is not smaller than an allowable value, it is judgedthat there is an abnormality so as to grasp an abnormal discharging ofthe coating liquid that the discharging of the coating liquid andbecomes broken during the coating operation or that the discharging ofthe coating liquid is not stopped at the stop timing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0028]FIG. 1 is a plan view showing the entire construction of a resistcoating-developing system of a semiconductor wafer, a resist coatingprocess unit for working the present invention being mounted to theresist coating-developing system;

[0029]FIG. 2 is a front view of the resist coating-developing systemshown in FIG. 1;

[0030]FIG. 3 is a back view of the resist coating-developing systemshown in FIG. 1;

[0031]FIG. 4 is an oblique view schematically showing the constructionof a main wafer transfer device mounted to the resist coating-developingsystem shown in FIG. 1;

[0032]FIG. 5 is a cross sectional view showing the entire constructionof the resist coating process unit mounted to the resistcoating-developing system shown in FIG. 1;

[0033]FIG. 6 is a plan view of the resist coating process unit shown inFIG. 4;

[0034]FIG. 7 is a cross sectional view showing another example inrespect of the mounting positions of a fiber sensor for projecting lightand a fiber sensor for receiving light, which are included in an opticalfiber sensor apparatus;

[0035]FIG. 8 is a cross sectional view showing still another example inrespect of the mounting positions of a fiber sensor for projecting lightand a fiber sensor for receiving light, which are included in an opticalfiber sensor apparatus;

[0036]FIG. 9 is a flow chart showing the process steps carried out inthe resist coating process unit;

[0037]FIG. 10 is a graph showing the operation timings of a drivingmotor, a pump, and an air operation valve when the coating of a resistsolution is carried out under the conventional control method and alsoshowing an ideal timing of the discharging of the resist solution;

[0038]FIG. 11 is a graph showing the operation timings of a drivingmotor, a pump, and an air operation valve in the case of generation ofthe delay in the discharging when the coating of a resist solution iscarried out under the conventional control method and also showing atiming of the discharging of the resist solution;

[0039]FIG. 12 is a graph showing the operation timings of a drivingmotor, a pump, and an air operation valve when the coating of a resistsolution is carried out under the control method for the embodiment ofthe present invention and also showing a timing of the discharging ofthe resist solution;

[0040]FIG. 13 is a block diagram for explaining the technique ofperforming the initial setting of an air operation valve by using anoptical fiber sensor apparatus;

[0041]FIG. 14 is a block diagram for explaining the technique ofgrasping an abnormal discharging of the resist solution by using anoptical fiber sensor apparatus; and

[0042]FIG. 15 is a cross sectional view showing the entire constructionof a resist coating process unit according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Some embodiments of the present invention will now be describedin detail with reference to the accompanying drawings.

[0044]FIG. 1 is a plan view schematically showing the resistcoating-developing system 1 including a resist coating process unitaccording to one embodiment of the coating process apparatus of thepresent invention. On the other hand, FIGS. 2 and 3 are a front view anda back view, respectively, of the resist coating-developing system 1shown in FIG. 1.

[0045] The resist coating-developing system 1 comprises a cassettestation 11 acting as a transfer station, a process station 12 includinga plurality of process units, and an interface station 13 for thedelivery of a wafer W between the process station 12 and a lightexposure device 14 arranged adjacent to the process station 12.

[0046] A cassette CR housing a plurality of wafers W, e.g., 25 wafers W,which are to be processed in the resist coating-developing system 1, istransferred from another system into the cassette station 11. Bycontraries, the cassette CR housing the wafers W after completion of theprocessing in the resist coating-developing system 1 is transferred fromthe cassette station 11 into the other system. Further, the cassettestation 11 serves to transfer the wafer W between the wafer cassette CRand the process station 12.

[0047] In the cassette station 11, a plurality of projections 20 a fordetermining the positions, i.e., five projections 20 a in FIG. 1, arearranged on a cassette table 20 in a manner to form a row extending inan X-direction, as shown in FIG. 1. The wafer cassette CR is disposed inthe position of the projection 20 a such that the wafer delivery port ofthe wafer cassette CR is allowed to face the process station 12.Incidentally, within the wafer cassette CR, the wafers W are arranged toassume a horizontal posture and arranged substantially in parallel inthe vertical direction (Z-direction), as shown in FIGS. 2 and 3.

[0048] A wafer transfer mechanism 21 is arranged in the cassette station11 so as to be positioned between the cassette table 20 and the processstation 12. The wafer transfer mechanism 21 includes a wafer transferpick 21 a movable in the arranging direction of the cassettes CR(X-direction) and in the arranging direction of the wafers W within thewafer cassette CR (Z-direction). The wafer transfer pick 21 a is alsoswingable in the θ-direction shown in FIG. 1. It follows that the wafertransfer pick 21 a is capable of gaining access selectively to any ofthe wafer cassettes CR and to a transition unit (TRS-G₃) arranged in athird process unit group G₃ included in the process station 12.

[0049] In the process station 12, the third process unit group G₃, afourth process unit group G₄, and a fifth process unit group G₅ arearranged on the back side of the system (in an upper portion in FIG. 1)in the order mentioned as viewed from the cassette station 11. Also, afirst main transfer section A₁ is arranged between the third processunit group G₃ and the fourth process unit group G₄. Likewise, a secondmain transfer section A₂ is arranged between the fourth process unitgroup G₄ and the fifth process unit group G₅. Further, a first processunit group G₁ and a second process unit group G₂ are arranged on thefront side of the system (lower portion in FIG. 1) in the ordermentioned as viewed from the cassette station 11.

[0050] As shown in FIG. 3, oven type process units, in which aprescribed processing is applied to the wafer W disposed on a table, arestacked one upon the other so as to form the third process unit groupG₃. To be more specific, stacked in the third process unit group G₃ arehigh temperature heat treating units (BAKE) for applying a prescribedheat treatment to the wafer W, high precision temperature control units(CPL-G₃) for applying a heat treatment to the wafer W under thetemperature control of a high precision, a temperature control unit(TCP), and the transition unit (TRS-G₃) acting as a delivery section ofthe wafer W between the cassette station 11 and the first main transfersection A₁. These process units are stacked one upon the other to formthe third process unit group G₃ of, for example, a 10-stage structure.Incidentally, a spare space is formed in the third process unit group G₃so as to be positioned in the third stage from the bottom. It ispossible to arrange a desired oven type process unit in the spare space.

[0051] Stacked on upon the other in the fourth process unit group G₄are, for example, pre-bake units (PAB) for applying a heat treatment tothe wafer W after the resist coating treatment, post-bake units (POST)for applying a heat treatment to the wafer W after the developingtreatment, and a high precision temperature control unit (CPL-G₄). Theseprocess units are stacked one upon the other so as to form the fourthprocess unit group G₄ of, for example, a 10-stage structure. Further,stacked one upon the other in the fifth process unit group G₅ are, forexample, post-exposure bake units (PEB) for applying a heat treatment tothe wafer W after the light exposure and before the developing treatmentand high precision temperature control units (CPL-G₅). These processunits are stacked one upon the other so as to form the fifth processunit group G₅ of, for example, a 10-stage structure.

[0052] As shown in FIGS. 1 and 3, a sixth process unit group G₆including an adhesion unit (AD) and a heating unit (HP) for heating thewafer W is arranged on the back side of the first main transfer sectionA₁. It is possible to allow the adhesion unit (AD) to have the functionof controlling the temperature of the wafer W.

[0053] A seventh process unit group G₇ including a peripheral lightexposure device (WEE) for selectively allowing the edge portion alone ofthe wafer W to be exposed to light and a thickness measuring device(FTI) for measuring the thickness of the resist film is arranged on theback side of the second main transfer section A₂. It is possible toarrange a plurality of peripheral light exposure devices (WEE) to form amulti-stage structure. Also, it is possible to arrange a heat treatingunit such as the heating unit (HP) on the back side of the second maintransfer section A₂ as on the back side of the first main transfersection A₁.

[0054] As shown in FIGS. 1 and 2, five spinner type process units eachconstituting a liquid supply unit in which a prescribed treatment isapplied to the wafer W disposed on a spin chuck SP within a cup (CP) arearranged to form a first process unit group G₁. For example, threeresist coating units (COT) and two bottom coating units (BARC) forforming an antireflection film for preventing the light reflectionduring the light exposure treatment are stacked one upon the other so asto form the first process unit group G₁ of, for example, a 5-stagestructure. On the other hand, five spinner type process units, e.g.,developing units (DEV), are stacked one upon the other so as to form asecond process unit group G₂ of a 5-stage structure.

[0055] A first main wafer transfer device 16 is arranged in the firstmain transfer section A₁. The first main wafer transfer device 16 iscapable of selectively gaining access to any of the process unitsarranged in the first process unit group G₁, the third process unitgroup G₃, the fourth process unit group G₄, and the sixth process unitgroup G₆. Also, a second main wafer transfer device 17 is arranged inthe second main transfer section A₂. The second main wafer transferdevice 17 is capable of selectively gaining access to any of the processunits arranged in the second process unit group G₂, the fourth processunit group G₄, the fifth process unit group G₅, and the seventh processunit group G₇.

[0056]FIG. 4 is an oblique view schematically showing the constructionof the first main wafer transfer device 16. As shown in the drawing, thefirst main wafer transfer device 16 comprises three arms, i.e., an arm 7a in the upper stage, an arm 7 b in the middle stage and an arm 7 c inthe lower stage, an arm support plate 51 mounted to the proximal endportion of each of the arms 7 a to 7 c (the support plate 51 mounted tothe arm 7 a alone being shown in the drawing), a base 52 engaged witheach of the arm support plates 51, a support section 53 for supportingthe base 52, etc., a motor (not shown) housed within the support section53, a rotatable rod 54 for joining the base 52 to the motor, supportrods 55 arranged on the sides of the first process unit group G₁ and thesecond process unit group G₂ and each having a sleeve 55 a formedtherein in a manner to extend in the vertical direction, a flange member56 slidably engaged with the sleeve 55 a and joined to the supportsection 53, and a lift mechanism (not shown) for moving the flangemember 56 in the vertical direction.

[0057] Rails (not shown) for the arm support plates 51 are formed on thebase 52 in a manner to extend in the direction parallel to thelongitudinal direction of the base 52 so as to permit each of the armsupport plates 51 to be slidable along the rail. Also, if the motorarranged within the support section 53 is rotated, the rotatable rod 54is rotated so as to permit the base 52 to be rotated within an X-Yplane. Further, since the support section 53 is mounted to the flangemember 56 movable in the Z-direction, the base 52 is also movable in theZ-direction.

[0058] Because of the particular construction described above, the arms7 a to 7 c of the first main wafer transfer device 16 are movable in anyof the X-direction, the Y-direction and the Z-direction, with the resultthat these arms 7 a to 7 c are capable of gaining access to any of theprocess units included in the first process unit group G₁, the thirdprocess unit group G₃, the fourth process unit group G₄, and the sixthprocess unit group G₆ as described previously.

[0059] Vertical members 59 a are mounted to both sides in the tipportion of the base 52. Also, a shielding plate 8 positioned between thearm 7 a and the arm 7 b for shielding the heat radiated from these arms7 a, 7 b is mounted to these vertical members 59 a. Further, a bridgingmember 59 b is mounted between these vertical members 59 a. A pair ofoptical sensors (not shown) are mounted to the center of the bridgingmember 59 b and to the tip portion of the base 52 so as to make itpossible to confirm the presence or absence of the wafer W on each ofthe arms 7 a to 7 c and to confirm the protrusion of the wafer W fromany of these arms 7 a to 7 c. It should be noted that the second mainwafer transfer device 17 is substantially equal in construction to thefirst main wafer transfer device 16 described above.

[0060] Incidentally, a wall section 57 shown in FIG. 4 constitutes apart of the housing of the second main wafer transfer section A₂ on theside of the first process unit group G₁. A window section 57 a formed inthe wall section 57 facilitates the wafer delivery between the processunits included in the first process unit group G₁. Also, four fans 58arranged on the bottom portion of the second main wafer transfer sectionA₂ serve to control the pressure, temperature and humidity within thesecond main wafer transfer section A₂.

[0061] A liquid temperature control pump 24 for supplying a prescribedprocess solution to the first process unit group G₁ is arranged betweenthe first process unit group G₁ and the cassette station 11. Likewise, aliquid temperature control pump 25 for supplying a prescribed processsolution to the second process unit group G₂ is arranged between thesecond process unit group G₂ and the interface section 13. Further,arranged are ducts 28, 29 for supplying a clean air from an airconditioner (not shown) arranged outside the resist coating-developingsystem 1 into the process unit groups G₁ to G₅.

[0062] The first process unit group G₁ to the seventh process unit groupG₇ are detachable for the maintenance operation. Also, the panel on theback side of the process station 12 is detachable or openable. Chemicalunits (CHM) 26 and 27 for supplying a prescribed process solution to thefirst process unit group G₁ and the second process unit group G₂ arearranged in the lowermost stages of the first process unit group G₁ andthe second process unit group G₂, respectively. Further, a centralcontrol section 19 for controlling the entire resist coating-developingsystem 1 is arranged in a lower portion of the cassette station 11.

[0063] The interface station 13 comprises a first interface station 13 aon the side of the process station 12 and a second interface station 13b on the side of the light exposure device 14. A first wafer transferbody 62 is arranged in the first interface section 13 a in a manner toface the open portion of the fifth process unit group G₅, and a secondwafer transfer body 63 movable in the X-direction is arranged in thesecond interface station 13 b.

[0064] Arranged on the back side of the first wafer transfer body 62 isan eighth process unit group G₈ including a peripheral light exposuredevice (WEE), an in-buffer cassette (INBR) for temporarily housing thewafer W that is to be transferred into the light exposure device 14, andan out-buffer cassette (OUTBR) for temporarily housing the wafer Wtransferred out of the light exposure device 14. These process units arestacked one upon the other in the order mentioned as viewed from above.A plurality of wafers W, e.g., 25 wafers W, can be housed in each of thein-buffer cassette (INBR) and the out-buffer cassette (OUTBR). Also,arranged on the front side of the first wafer transfer body 62 is aninth process unit G₉ including a transition unit (TRS-G₉) and two highprecision temperature control units (CPL-G₉), which are stacked one uponthe other in the order mentioned as viewed from above.

[0065] The first wafer transfer body 62 is provided with a fork 62 amovable in the Z-direction, swingable in the θ-direction and movableback and forth within an X-Y plane. The fork 62 a is capable of gainingaccess to any of the process units included in the fifth process unitgroup G₅, the eighth process unit group G₈, and the ninth process unitgroup G₉ so as to make it possible to transfer the wafer W between theprocess units included in these process unit groups.

[0066] The second wafer transfer body 63 is movable in the X-directionand Z-direction, swingable in the θ-direction and provided with a fork63 a movable back and forth within an X-Y plane for delivering the waferW. The fork 63 a is capable of gaining access to each of the processunits included in the ninth process unit group G₉, and to an in-stage 14a and an out-stage 14 b included in the light exposure device 14 so asto make it possible to transfer the wafer W among these members.

[0067] In the resist coating-developing system 1 of the constructiondescribed above, unprocessed wafers W are taken out one by one from thewafer cassette CR by the wafer transfer mechanism 21 so as to betransferred into the transition unit (TRS-G₃). Then, after a temperaturecontrol treatment is applied to the wafer W in the temperature controlunit (TCP), an antireflection film is formed on the wafer W in thebottom coating unit (BARC) belonging to the first process unit group G₁,followed by applying a heat treatment to the wafer W in the heating unit(HP) and subsequently applying a baking treatment to the wafer W in thehigh temperature heat treating unit (BAKE). It is possible to apply anadhesion treatment to the wafer W in the adhesion unit (AD) beforeformation of the antireflection film on the wafer W in the bottomcoating unit (BARC). It is also possible to apply an adhesion treatmentto the wafer W without forming an antireflection film on the wafer W.Then, after the temperature of the wafer W is controlled in the highprecision temperature control unit (CPL-G₄), the wafer W is transferredinto the resist coating unit (COT) belonging to the first process unitgroup G₁ for application of the coating treatment with a resistsolution. Further, a pre-bake treatment is applied to the wafer W in thepre-bake unit (PAB) arranged in the fourth process unit group G₄,followed by applying a peripheral light exposure treatment to the waferW in the peripheral light exposure device (WEE) and subsequentlycontrolling the temperature of the wafer W in the high precisiontemperature control unit (CPL-G₉), etc. Then, the wafer W is transferredby the second wafer transfer body 63 into the light exposure device 14.The exposed wafer W in the light exposure device 14 is transferred bythe second wafer transfer body 63 into the transition unit (TRS-G₉) and,then, further transferred by the first wafer transfer body 62 into thepost-exposure bake unit (PEB) belonging to the fifth process group G₅for application of the post-exposure bake treatment to the wafer W.Further, the wafer W is transferred into the developing unit (DEV)belonging to the second process unit group G₂ for developing the waferW, followed by applying a post-bake treatment to the wafer W in thepost-bake unit (POST). Still further, a temperature control treatment isapplied to the wafer W in the high precision temperature control unit(CPL-G₃), followed by transferring the wafer W onto a prescribedposition within the wafer cassette CR arranged in the cassette station11 through the transition unit (TRS-G₃).

[0068] A resist coating process unit (COT) according to one embodimentof the present invention will now be described with reference to FIGS. 5to 8.

[0069] The resist coating process unit (COT) comprises a casing 70provided with an opening 70 a through which the arms 7 a to 7 c of themain wafer transfer device 16 are allowed to pass. A cup CP constitutinga container for housing the wafer W therein is arranged within thecasing 70. Further, a spin chuck 71 for horizontally holding thereon thewafer W by the vacuum suction is arranged within the cup CP. The spinchuck 71 can be rotated by a driving motor 72 such as a pulse motorarranged below the cup CP, and the rotating speed of the spin chuck 71can be controlled optionally. An exhaust pipe 73 is connected to acentral region in the bottom portion of the cup CP, and a liquiddischarge pipe 74 is connected to an outer region in the bottom portionof the cup CP. The gas within the cup CP is exhausted through theexhaust pipe 73, and the resist solution and the solvent scatteredduring the coating treatment are discharged to the outside through theliquid discharge pipe 74. Incidentally, the spin chuck 71 can be movedin the vertical direction by a lift mechanism such as an air cylinder(not shown).

[0070] A discharging head 80 is arranged above the spin chuck 71 so asto be movable between a position right above the spin chuck 71 and aretreating position. The discharging head 80 is connected to a drivingmechanism 83 with an arm 81 interposed therebetween so as to be movablein the X-direction, the Y-direction and the Z-direction shown in FIGS. 5and 6. Incidentally, the discharging head 80 is detachable from the arm81.

[0071] The discharging head 80 includes a base member 82 and isconstructed such that a solvent discharging nozzle 85 for supplying asolvent capable of dissolving a resist solution and a resist solutiondischarging nozzle 90 for supplying a resist solution constituting acoating liquid are mounted close to each other to the base member 82.The solvent capable of dissolving the resist solution permits improvingthe wettability of the resist solution so as to lower the consumption ofthe resist. It is possible for the solvent capable of dissolving theresist solution to constitute a solvent of the resist solution. However,the solvent capable of dissolving the resist solution is not limited tothe solvent of the resist solution, and a thinner is typically used asthe solvent capable of dissolving the resist solution.

[0072] Mounted to the discharging head 80 are a pipe (not shown) forcirculating a temperature control fluid for maintaining constant thetemperature of the resist solution discharged from the resist solutiondischarging nozzle 90 and another pipe (not shown) for circulating atemperature control fluid for maintaining constant the temperature ofthe solvent discharged from the solvent discharging nozzle 85.

[0073] A resist solution supply pipe 91 is connected to the resistsolution discharging nozzle 90, and the resist solution supply pipe 91is allowed to communicate with a resist solution tank 92 housing aresist solution. Connected to the resist solution supply pipe 91 are asuck back valve 93, an air operation valve 94, a bubble removingmechanism 95 for separating and removing bubbles from the resistsolution, a filter 96, and a pump 97 in the order from the downstreamside. It is desirable to use as the pump 97 a bellows pump including ashrinkable bellows or a tubephragm pump including a tubephragm that isshrunk by the liquid pressure so as to send forth the resist solution. Asolvent supply pipe 86 is connected to the solvent discharging nozzle 85such that the solvent supplied from a solvent supply source (not shown)flows through the solvent supply pipe 86 so as to be discharged from thesolvent discharging nozzle 85.

[0074] As shown in FIG. 6, a holding section 75 capable of holding fourdischarging heads 80, which basically have the same construction, isarranged outside the cup CP within the casing 70. Arranged in theholding section 75 is an inserting section (solvent drain section) forputting the nozzle port of each nozzle under a solvent atmosphere so asto prevent the nozzle port of each nozzle from being dried andsolidified. Each discharging head 80 can be mounted to the tip portionof the arm 81 by a mounting section 76. Different kinds of resistsolutions can be supplied into the discharging heads 80. One selecteddischarging head 80 is mounted to the arm 81 and is taken from theholding section 75. As described above, it is possible for the arm 81 tobe moved by the driving mechanism 83 in three dimensional directions,i.e., in the X-, Y- and Z-directions, such that the discharging head 80mounted to the arm 81 taken out of the holding section 75 is moved to aprescribed position right above the wafer W in processing the wafer W.

[0075] In the example shown in FIG. 6, the solvent discharging nozzle 85and the resist solution discharging nozzle 90 are mounted to eachdischarging head 80. However, it is also possible to mount the resistsolution discharging nozzle 90 alone to each discharging head 80 and tomount a single solvent discharging nozzle 80 for the common use with theresist solution discharging nozzles 90 of the discharging heads 80. Inthis case, it is possible to arrange separately a driving arm for thesolvent discharging nozzle 85. It is also possible to mount in advancethe solvent discharging nozzle 85 to the arm 81 so as to permit thesolvent discharging nozzle 85 to be movable together with onedischarging head 80 that has been selected.

[0076] The resist coating process unit (COT) according to thisembodiment of the present invention comprises an optical fiber sensorapparatus 100. The optical fiber sensor apparatus 100 includes anoptical fiber sensor 101 for projecting light, which is mounted to thesolvent discharging nozzle 85, an optical fiber sensor 102 for receivinglight, which is mounted to a mounting bracket 87 mounted to facedownward to the central portion of the arm 81, a light source 103 towhich the optical fiber sensor 101 for projecting light is connected, anamplifier 104 for amplifying the light received by the optical fibersensor 102 for receiving light, and a sensor controller 105 forcontrolling the entire optical fiber sensor apparatus such as theprocessing of the received optical signal. The light projecting opticalfiber sensor 101 projects light such that the projected light traversesthe discharged stream of the resist solution in the case where theresist solution is being discharged from the resist solution dischargingnozzle 90. The light receiving optical fiber sensor 102 receives thelight projected from the optical fiber sensor 101 for projecting lightand, then, reflected from the wafer W. Since the case where the resistsolution is being discharged from the resist solution discharging nozzle90 differs from the case where the resist solution is not dischargedfrom the resist solution discharging nozzle 90 in the amount of thelight detected by the light receiving optical fiber sensor 102, it ispossible for the optical fiber sensor apparatus 100 to detect theinitiation of the discharging of the resist solution.

[0077] The resist coating process unit (COT) according to thisembodiment of the present invention comprises a controller 110 as shownin FIG. 5. It is possible for the controller 110 to control the drivingmotor 72 for rotating the spin chuck 71, the air operation valve 94 andthe pump 97. Also, a setting device 111 for setting, for example, thecontrol conditions in the controller 110 is connected to the controller110. Further, the sensor controller 105 is connected to the controller110. A control signal is transmitted from the sensor controller 105 tothe optical fiber sensor apparatus 100, and a signal transmitted fromthe optical fiber sensor apparatus 100 is received by the sensorcontroller 105.

[0078] When the optical fiber sensor apparatus 100 has detected that theresist solution discharging nozzle 90 has started discharging the resistsolution therefrom, the detected signal is transmitted to the controller110 and the controller 110 calculates the resist solution dischargingtiming based on the detected signal. Also, the controller controls atleast one of the driving motor 72 for rotating the spin chuck 71, theair operation valve 94 and the pump 97 based on the calculateddischarging timing of the resist solution. As a result, the timingbetween the rotation of the wafer W and the discharging of the resistsolution and the discharging time of the resist solution, which areimportant for the coating operation of the resist solution, arecontrolled appropriately.

[0079] In this case, it is possible for the controller 110 to performthe control operation automatically based on the calculated dischargingtiming of the resist solution. Alternatively, it is also possible forthe operator to set the parameters of the setting device 111 based onthe grasped discharging timing of the resist solution.

[0080] It is possible to mount the light projecting optical fiber sensor101 and the light receiving optical fiber sensor 102 included in theoptical fiber sensor apparatus 100 to the cup CP, as shown in FIG. 7. Inthis case, it is possible to allow the light projected from the lightprojecting optical fiber sensor 101 to reach the receiving optical fibersensor 102 without being reflected by the wafer W.

[0081] In addition, it is possible to construct the optical fiber sensorapparatus 100 to detect the discharging timing of the resist solutionnot only in the case of the actual discharging of the resist solutiononto the wafer W as in the description given above but also in the caseof the dummy dispense that does not necessitate the presence of thewafer W. As shown in FIG. 8, it is possible to mount the lightprojecting optical fiber sensor 101 and the light receiving opticalfiber sensor 102 to a drain case 121 included in a solvent drain section120 of the holding section 75 outside the cup CP so as to detect thedischarging timing of the resist solution in the case of the dummydispense.

[0082] In the example shown in FIG. 5, it is difficult for the reflectedlight to reach the light receiving optical fiber sensor 102 after thedischarging of the resist solution, with the result that the operationof the optical fiber sensor apparatus 100 is limited to the detection ofthe discharging initiation of the resist solution. However, in theexample shown in each of FIGS. 7 and 8, the optical fiber sensorapparatus 100 is free from the limitation given above and, thus, is ofcourse capable of detecting the discharging initiation of the resistsolution and is also capable of detecting that the resist solution hasceased to be discharged. In this case, the controller 110 is capable ofcontrolling based on the detected signal at least one of the drivetiming for stopping the pump 97, the operation timing of the airoperation valve 94, and the timing for stopping the rotation of thedriving motor 72.

[0083] Incidentally, the controller 110 actually controls the suck backvalve 93 and other members relating to the coating process of the resistsolution such as a solvent supply system (not shown), though thedescription thereon is omitted herein. Also, the suck back valve 93serves to suck the resist solution remaining by the surface tension onthe inner wall portion at the tip of the resist solution dischargingnozzle 90 back into the resist solution discharging nozzle 90 after thedischarging of the resist solution from the resist solution dischargingnozzle 90 so as to prevent the remaining resist solution from beingsolidified.

[0084] The operation and control of the resist solution coating processperformed by the resist coating process unit (COT) constructed asdescribed above will now be described with reference to the flow chartshown in FIG. 9.

[0085] If the wafer W is transferred by any of the arms 7 a, 7 b and 7 cof the first main wafer transfer device 16 through the opening 70 a ofthe casing 70 to reach a position right above the cup CP within theresist coating process unit (COT), the wafer W is sucked by vacuumsuction by the spin chuck 71 moved upward by the lift mechanism (notshown). After the wafer W is sucked by the spin chuck 71 by the vacuumsuction, the main wafer transfer mechanism 22 brings back the arm 7 a, 7b, or 7 c from within the resist coating process unit (COT) so as tofinish the delivery of the wafer W into the resist coating process unit(COT) (STEP 1).

[0086] Then, the spin chuck 71 is moved downward until the wafer W islocated at a prescribed position within the cup CP. Under thiscondition, the spin chuck 71 is rotated by the driving motor 72 at arotating speed of about 1,000 rpm so as to make the temperature of thewafer W uniform (STEP 2).

[0087] After the temperature of the wafer W is made uniform, thedischarging head 80 is moved in the Y-direction by the driving mechanism83 to reach a position right above the wafer W. When the dischargingport of the solvent discharging nozzle 85 has been moved to reach aposition substantially above the center of the spin chuck 71(substantially above the center of the wafer W), performed is a pre-wetprocessing in which a solvent dissolving the resist such as a thinner issupplied onto substantially the center on the surface of the wafer Wthat is held stationary, and the wafer W is rotated at a prescribedrotating speed, preferably not higher than 1,000 rpm, so as to spreadthe solvent supplied onto the central portion on the surface of thewafer W over the entire surface region of the wafer W (STEP 3). As aresult, the wettability of the resist solution is improved so as todecrease the amount of the resist solution discharged onto the wafer W.

[0088] In the next step, the discharging head 80 is moved by the drivingmechanism 83 in the Y-direction until the discharging port of the resistsolution discharging nozzle 90 reaches a point substantially right abovethe center of the spin chuck 71, i.e., substantially right above thecenter of the wafer W. Under this condition, the rotating speed of thewafer W is increased to reach a prescribed value, and the resistsolution is supplied from the discharging port of the resist solutiondischarging nozzle 90 onto substantially the center on the surface ofthe rotating wafer W. As a result, the resist solution is centrifugallydiffused outward on the wafer surface so as to coat the entire surfaceof the wafer W with the resist solution (STEP 4). In carrying out theresist coating treatment, the wafer W is rotated at a relatively highspeed in the initial stage while supplying the resist solution onto thewafer surface so as to expand the resist solution supplied onto thewafer surface. To be more specific, it is desirable to rotate the waferat a speed of 2,000 to 6,000 rpm in the case of the wafer having adiameter of 200 mm, and at a speed of 1,000 to 4,000 rpm in the case ofthe wafer having a diameter of 300 mm. Then, the supply of the resistsolution is stopped and the rotating speed of the wafer W is lowered. Asa result, the function of controlling the thickness of the resist filmis produced so as to promote the effect of making uniform the thicknessof the resist film on the wafer surface. It should be noted in thisconnection that, when the rotating speed of the semiconductor wafer W islowered, the force directed toward the center of the wafer W is exertedon the resist solution on the wafer W by the deceleration. In addition,since the rotating speed of the wafer W is low, the resist solution onthe wafer W is dried slowly. It follows that the function of controllingthe thickness of the resist film is exhibited as described above. To bemore specific, the amount of the resist solution scattered toward theoutside of the wafer W is suppressed by the force directed toward thecenter of the wafer W, which is produced by the deceleration. Likewise,the resist solution is held on the outer circumferential portion of thewafer W as in the central portion. It follows that the thickness of theresist film is made more uniform. It is desirable for the rotating speedof the wafer W to be 50 to 1,000 rpm in this case. Particularly, wherethe rotating speed of the wafer W is not higher than 500 rpm, the dryingof the resist solution scarcely proceeds, leading to a higher degree offreedom in terms of the film thickness control. The holding time in thiscase is set appropriately not to exceed, for example, three seconds.Incidentally, it is not absolutely necessary to lower the rotating speedof the wafer W. In other words, the rotating speed of the wafer W islowered, as required.

[0089] In the next step, the rotating speed of the wafer W is increasedso as to centrifugally remove the extra resist solution (STEP 5). It isdesirable to set the rotating speed in this stage at 1,500 to 4,000 rpmin the case of the wafer having a diameter of 200 mm, and at 1,000 to3,000 rpm in the case of the wafer having a diameter of 300 mm.

[0090] Then, the rotation of the wafer W is continued so as to dry theresist film (STEP 6). It is desirable to set the rotating speed in thisstage at 1,000 to 2,000 rpm in the case of the wafer having a diameterof 200 mm, and at 500 to 1,500 rpm in the case of the wafer having adiameter of 300 mm. The resist coating process is finished after thedrying process is carried out for a prescribed period of time.

[0091] The control in the resist coating process will now be describedin detail.

[0092] In order to form the resist film at a high accuracy and at a highuniformity in the film thickness, it was customary to control strictlythe rotation of the driving motor 72, the operation of the pump 97, andthe operation of the air operation valve 94, which is an opening-closingvalve, based on a software. FIG. 10 is a graph showing the ideal timingsof these operations and the discharging timing of the resist solution inthe case of carrying out the resist solution coating under theconventional control method. In the first step, a signal to start thedriving, a signal to start the discharge operation, and an open signalare simultaneously transmitted from the controller 110 to the drivingmotor 72, the pump 97 and the air operation valve 94, respectively. As aresult, the rotation of the spin chuck 71 is started and the rotatingspeed of the spin chuck 71 is increased. The pump 97 begins to dischargethe resist solution substantially simultaneously with the instructiongiven from the controller 110. On the other hand, the air operationvalve 94 is opened slightly later, and the discharging of the resistsolution is started immediately after the air operation valve 94 isopened. The discharging of the resist solution is controlled such thatthe discharging is started while the wafer W, which is rotated togetherwith the spin chuck 71, is being rotated at a low speed. After thedischarging time t₀ on the signal, a signal to finish the dischargeoperation and a close signal are transmitted simultaneously from thecontroller 110 to the pump 97 and the air operation valve 94,respectively, as shown in FIG. 10. Slightly after these signals aretransmitted, the air operation valve 94 is actually closed. At thisstage, a signal to stop the driving is transmitted to the driving motor72 so as to lower the rotating speed of the wafer W. In this case, eachof the open time t₁ of the air operation valve 94 and the actualdischarge time t₂ substantially coincides with the discharge time t₀and, thus, no problem is generated.

[0093] However, the three resist coating process units (COT) are stackedone upon the other as described previously, and the resist solution issupplied in general to the resist solution discharging nozzles 90 ofthese units (COT) through a common pipe. As a result, the time to startthe discharging of the resist solution from the resist solutiondischarging nozzle 90 from the transmission of the open signal from thecontroller 110 to the air operation valve is rendered nonuniform by thedifference in head among the resist coating process units (COT) and bythe individual variation of the pump or the air operation valve, withthe result that the time to start the discharging of the resist solutionfrom the time for the air operation valve to have been opened isretarded from the ideal state shown in FIG. 10, as shown in FIG. 11. Thedelay time Δt is increased in some cases such that the rotating speed ofthe wafer W is increased to reach about the maximum speed at the timewhen the discharging of the resist solution is actually started. If theresist solution is discharged under the high rotating speed of the waferW, the thickness of the resist film is much deviated from the set value.Also, in this case, the actual discharging time t₂′ of the resistsolution is rendered shorter than the time t₂ referred to previously bythe time corresponding to the delay in the starting of the resistsolution discharging. What should be noted is that the thickness of theresist film in the peripheral portion of the wafer W is decreased withincrease in the delay time Δt and with shortening in the dischargingtime so as to render poor the uniformity in the thickness of the resistfilm.

[0094] In order to avoid the problems described above, the starting ofthe resist solution discharging is detected in the present invention byusing the optical fiber sensor apparatus 100, and the resist coatingprocess is controlled on the basis of the start timing of the resistsolution discharging, which is calculated based on the detected signal,as described previously.

[0095] To be more specific, the controller 110 controls at least one ofthe drive start timing of the driving motor 72 for rotating the spinchuck 71, the drive timing of the air operation valve 94, and the drivetiming of the pump 97 on the basis of the start timing of the resistsolution discharging, which is calculated from the signal detected bythe optical fiber sensor apparatus 100. For example, as shown in FIG.12, the start timing of the resist solution discharging is calculated onthe basis of the signal detected by the optical fiber sensor apparatus100, and the drive start timing of the driving motor 72 is retarded bythe controller 110 based on the calculated value when the resist coatingprocess of the next wafer is performed. Of course, it is possible toadvance the drive start timing of the pump 97 and/or the timing ofopening the air operation valve 94. Also, the controller 110 calculatesthe delay time Δt from the signal to start the resist solutiondischarging, and a control signal is transmitted to the pump 97 and theair operation valve 94 so as to extend the discharging time of theresist solution by the time corresponding to the delay time Δt, therebymaking the actual discharging time t₂″ substantially equal to time t₂.Also, the timing to stop the driving motor 72 is controlled based on theactual discharging time of the resist solution.

[0096] As described above, the time when the resist solution began to beactually discharged from the resist solution discharging nozzle 90 isdetected in the present invention, and the coating process of the resistsolution is controlled on the basis of the detected signal. It followsthat the various conditions can be controlled under the state that thetime when the resist solution was actually discharged is grasped so asto make it possible to make up for the nonuniformity in the start timingof the resist solution discharging caused by, for example, thedifference in the head of the resist solution discharging nozzle 90 andthe individual variation of the pump 97 or the air operation valve 94.

[0097] To be more specific, the starting of the resist solutiondischarging from the resist solution discharging nozzle 90 is detectedby the optical fiber sensor apparatus 100, and at least one of the drivestart timing of the driving motor 72 for rotating the spin chuck 71, thedrive timing of the air operation valve 94 and the drive timing of thepump 97 is controlled on the basis of the start timing of the resistsolution discharging, which is calculated based on the signal detectedby the optical fiber sensor apparatus 100. It follows that it ispossible to prevent the difficulty that the resist film fails to have aprescribed thickness because the rotating speed of the wafer W isexcessively high at the discharging time of the resist solution. Itshould also be noted that the delay time Δt between the time oftransmitting an open signal to the air operation valve 94 based on thesignal denoting the detection of start-up of the resist solutiondischarging and the time of actual discharging of the resist solution iscalculated in the present invention, and the pump 97 and the airoperation valve 94 are controlled based on the calculated delay time Δtso as to extend the discharging time of the resist solution to conformwith the prescribed time. It follows that it is possible to rendersubstantially constant the actual discharging time of the resistsolution so as to further improve the uniformity in the thickness of theresist film. What should also be noted is that the stop timing of thedriving motor 72 is also controlled on the basis of the delay time Δt soas to further improve the uniformity in the thickness of the resistfilm.

[0098] On the other hand, it is also possible for the time between thetransmission of the close signal to the air operation valve 94 and thetime when the discharging of the resist solution from the resistsolution discharging nozzle 90 is actually stopped to be made nonuniformby various factors. If the time required for stopping the discharging ofthe resist solution is nonuniform, the actual discharging time isrendered nonuniform in practice even if the actual discharging time ofthe resist solution is controlled based on the signal to start thedischarging of the resist solution as described above.

[0099] In such a case, it is detected by the optical fiber sensorapparatus 100 that the discharging of the resist solution has beenstopped, and at least one of the drive stop timing of the pump 97, theoperation timing of the air operation valve, and rotation stop timing ofthe driving motor 72 is controlled based on the signal detected by theoptical fiber sensor apparatus 100. As a result, it is possible toimprove markedly the nonuniformity of the actual discharging time. To bemore specific, the controller 110 calculates the stop timing of thedischarging of the resist solution based on a signal denoting the stopof the discharging, which is detected by the optical fiber sensorapparatus 100, and at least one of the drive stop timing of the pump 97,the operation timing of the air operation valve 94, and the rotationstop timing of the driving motor 72 is controlled so as to permit thedischarging of the resist solution to be stopped at an appropriatetiming based on the calculated value in performing the next process ofcoating the wafer with the resist solution.

[0100] It should be noted, however, that, in the case of the apparatusconstructed as shown in FIG. 5, it is impossible to detect the stop ofthe discharging of the resist solution. Therefore, the detection of thestop of the discharging of the resist solution is limited to the casewhere th optical fiber sensor 100 is mounted as shown in FIGS. 7 and 8.

[0101] It is possible to control the start timing of the discharging ofthe resist solution and the actual discharging time with a high accuracyby the control method described above. Further, in the case of using theoptical fiber sensor apparatus 100, a high precision in the filmthickness and a high uniformity of the film thickness can be achieved byemploying the techniques described below in addition to or separatelyfrom the control method described above.

[0102] In the first technique, the state in starting the discharging ofthe resist solution and/or the state in stopping the discharging isdetected by the optical fiber sensor apparatus 100 so as to control thespeed of opening and/or closing the air operation valve 94 to fallwithin an allowable range. To be more specific, if the air operationvalve 94 is opened at an excessively high speed, the resist solution is,for example, once sucked and, then, discharged. On the other hand, ifthe air operation valve 94 is opened at an excessively low speed, adifficulty such as a liquid dripping is brought about. Also, if the airoperation valve 94 is closed at an excessively high speed, the state instopping the discharging of the resist solution is rendered unstable. Onthe other hand, if the air operation valve 94 is closed at anexcessively low speed, a difficulty such as a liquid dripping is broughtabout. It follows that it is important to control in advance the speedof opening and/or closing the air operation valve so as to permit thestate in starting the discharging of the resist solution and/or thestate in stopping the discharging to fall within an allowable range.

[0103] As shown in, for example, FIG. 13, the air operation valve 94includes a container 121, a valve body 122 arranged movable in thevertical direction within the container 121, a valve seat 123 positionedbelow the valve body 122, and a resist solution flowing section 124. Theresist solution flowing section 124 includes a resist solutionpassageway 125 connected to the resist solution supply pipe 91. A resistsolution inlet port 126 and a resist solution outlet port 127 are opento the valve seat 123 from the resist solution passageway 125. Under theclosed state that the valve body 122 abuts against the valve seat 123,the flow of the resist solution is shielded, and resist solution isallowed to flow under the open state that the valve body 122 ispositioned apart from the valve seat 123. A partition member 128 forpartitioning the inner space of the container 121 into an upper spaceand a lower space is arranged movable in the vertical direction, and thevalve body 122 is formed integral with the partition member 128 in amanner to hang from the partition member 128. The air is introduced froman air introducing port 129 formed in the side wall of the container 121into the container 121 through an air introducing pipe 130 so as to moveupward the partition member 128. As a result, the valve body 122 is alsomoved upward so as to open the valve 94. The introduction of the air isperformed by operating an inlet side solenoid valve 132 mounted to theair introducing pipe 130. Also, an air discharge port 134 is formed inthe side wall of the container 121, and an air discharge pipe 135 isconnected to the air discharge port 134. When the valve 94 is closed,the air supply is stopped and a discharge side solenoid valve 136mounted to the air discharge pipe 135 is operated so as to discharge theair within the container 121. A coil spring 131 urging downward thepartition member 128 is mounted within the container 121 above thepartition member 128. Since the valve 94 is of a normally closedstructure that the air operation valve 94 is kept closed in the casewhere the air is not introduced into the container 121 and when the airis discharged as described above, the valve 94 is closed by dischargingthe air from within the container 121 through the air discharge pipe 135after the air operation valve 94 is opened.

[0104] The inlet side solenoid valve 132 and the outlet side solenoidvalve 136 are operated by operating a valve controller 140. On the otherhand, the valve controller 140 is controlled by the controller 110described previously. It follows that the opening speed and the closingspeed of the air operation valve 94 are controlled by allowing the valvecontroller 140 to control the inlet side solenoid valve 132 and theoutlet side solenoid valve 136, respectively, in response to theinstruction given from the controller 110.

[0105] Where the opening speed of the air operation valve 94 is setinitially, the air operation valve 94 is opened at various speeds so asto detect the initial state of the discharging of the resist solution bythe optical fiber sensor apparatus 100, and the optimum opening speed isautomatically selected from among the values falling within an allowablerange. When the resist solution is actually discharged, the optimumopening speed thus selected used as the set value. This is also the casewith the initial setting of the closing speed in the case of closing theair operation valve 94. Specifically, the air operation valve 94 isclosed at various closing speeds, and the state in stopping thedischarging of the resist solution is detected by the optical fibersensor apparatus 100 so as to automatically select the optimum closingspeed from among the values falling within an allowable range. When theresist solution is actually discharged, the optimum closing speed thusselected is used as the set value. In this fashion, the state at theinitiation of the discharging of the resist solution and/or the state atthe finishing time of discharging can be set in advance to fall withinallowable ranges so as to make it possible to avoid the detrimentaleffects given by the state at the initiation of the discharging of theresist solution and/or the state at the finishing time of thedischarging to the accuracy and the uniformity of the resist filmthickness. In this case, the delay time between the transmission of asignal to the air operation valve 94 and actual initiation of thedischarging of the resist solution and/or the actual finishing time ofthe discharging is dependent on the opening speed and/or the closingspeed of the air operation valve 94. Therefore, after the opening speedand/or the closing speed of the air operation valve 94 is set, the setvalue of the corresponding delay time is determined. Where the state instarting alone the discharging of the resist solution is madeappropriate by the first technique, it is possible to use the opticalfiber sensor apparatus 100 shown in any of FIGS. 5, 7 and 8. On theother hand, in the case of making appropriate the state in finishing thedischarging, used is the optical fiber sensor apparatus 100 shown inFIG. 7 or 8.

[0106] The second technique will now be described.

[0107] The second technique is for grasping the abnormal discharging ofthe resist solution such as the situation that the supply of the resistsolution becomes broken during the coating operation or the situationthat discharging of the resist solution is not stopped at the stoptiming. To be more specific, the actual discharging time during whichthe discharging of the resist solution is detected by the optical fibersensor apparatus 100 is measured by a timer 141, and the actualdischarging time thus measured is compared with the set time for thedischarging of the resist solution, as shown in FIG. 14. It is judgedthat there is an abnormality in the case where there is a differencelarger than an allowable value between the actual discharging time andthe set time. As a result, it is possible to stop the coating processwhen there is an abnormal discharging of the resist solution so as tomake it possible to avoid the detrimental effects given by the abnormaldischarging of the resist solution to the accuracy and the uniformity ofthe resist film thickness. In the case of the second technique, it isnecessary to grasp the state that the resist solution is being actuallydischarged. Therefore, the optical fiber sensor apparatus 100 isarranged as shown in FIG. 7 or 8.

[0108] A resist coating process unit (COT) according to anotherembodiment of the present invention will now be described with referenceto FIG. 15.

[0109] The embodiment shown in FIG. 15 differs from the embodimentdescribed above in that a CCD camera system 150 is used as the detectingapparatus in place of the optical fiber sensor apparatus 100 used in theembodiment described above.

[0110] As shown in FIG. 15, the CCD camera system 150 includes a CCDcamera 151 for photographing the stream of the resist solutiondischarged from the resist solution discharging nozzle 90, a cameracontrol section 152 for controlling the operation of the CCD camera 151and for controlling the information, an image process section 153, and amonitor 154. The image photographed by the CCD camera 151 is transmittedto the image process section 153 via the camera control section 152 forapplication of a prescribed image processing to the photographed image.Then, the information on the image processing is transmitted to thecamera control section 152, with the result that the initiation of thedischarging of the resist solution and/or the finish of the dischargingof the resist solution is grasped. Also, the image in this stage isdisplayed as required on the monitor 154. As a result, the actualinitiation of the discharging of the resist solution and/or the actualfinish of the discharging of the resist solution can be detected so asto make it possible to achieve the control similar to that achieved inthe embodiment described previously. It follows that it is possible toprevent the inconveniences causing the fluctuation in the thickness ofthe film such as the situation that the target substrate to be processedis rotated at an excessively high speed at the discharging stage of theresist solution and the situation that the actual discharging time isshort.

[0111] It should be noted that the embodiments described above aresimply intended to clarify the technical idea of the present invention.Naturally, the technical scope of the present invention should not beconstrued solely on the basis of the specific embodiments describedabove. In other words, the present invention can be worked in variouslymodified fashions on the basis of the spirit of the present inventionand within the scope defined in the accompanying claims.

[0112] For example, each of the embodiments described above covers thecase where an optical fiber sensor apparatus or a CCD camera system isused as the detecting apparatus for detecting the start or stop of thedischarging of the resist solution. However, it is also possible to usean optical sensor other than the optical fiber sensor or another opticaldetecting apparatus. Also, each of the embodiments described abovecovers the case where a resist solution is used as the coating liquid.However, it is also possible to use a coating liquid for forming a filmby a rotary coating process, i.e., for forming, for example, anantireflection film or an interlayer insulating film, and other coatingliquids. Further, in each of the embodiments described above, asemiconductor wafer is used as the target substrate to be processed.However, it is also possible to use other target substrates such as anLCD substrate and a reticle substrate for a mask.

What is claimed is:
 1. A coating process method in which a coatingliquid is discharged onto the surface of a target substrate to beprocessed while rotating the target substrate so as to expand thecoating liquid radially outward on the target substrate and, thus, toform a coated film, comprising the steps of: detecting that the actualdischarging of a coating liquid from a coating liquid discharging nozzleis started and/or stopped; and controlling the coating treatment on thebasis of a signal of the detection.
 2. The coating process methodaccording to claim 1, wherein the start and/or stop of the dischargingof the coating liquid is detected by using an optical sensor.
 3. Thecoating process method according to claim 2, wherein the optical sensorincludes an optical fiber sensor for projecting light and an opticalfiber sensor for receiving light.
 4. The coating process methodaccording to claim 1, wherein the start and/or stop of the dischargingof the coating liquid is detected by using a CCD camera.
 5. The coatingprocess method according to claim 1, wherein the start of thedischarging of the coating liquid is detected when the coating liquid isdischarged from the coating liquid discharging nozzle onto the targetsubstrate.
 6. The coating process method according to claim 1, whereinthe start of the discharging of the coating liquid is detected when thecoating liquid discharging nozzle discharges the coating liquid from aposition retreated from the target substrate.
 7. A coating processmethod in which a coating liquid is discharged onto the surface of atarget substrate to be processed while rotating the target substrate soas to expand the coating liquid radially outward on the target substrateand, thus, to form a coated film, comprising the steps of: detectingthat the actual discharging of a coating liquid from a coating liquiddischarging nozzle is started; and controlling based on a signal of thedetection at least one of the drive timing of a pump for allowing thecoating liquid to be discharged from the coating liquid dischargingnozzle, the operation timing of a valve mounted to a pipe for supplyingthe coating liquid into the coating liquid discharging nozzle, and therotation starting or stopping timing of the target substrate.
 8. Thecoating process method according to claim 7, wherein, in the controllingstep, a delay time from the timing of actually discharging the coatingliquid is obtained based on the detected signal denoting that thedischarging of the coating liquid has been started, and at least one ofthe drive timing of the pump for allowing the coating liquid to bedischarged from the coating liquid discharging nozzle, the operationtiming of a valve mounted to a pipe for supplying the coating liquidinto the coating liquid discharging nozzle, and the start or stop timingof the rotation of the target substrate is controlled based on the delaytime from the timing of actually discharging the coating liquid.
 9. Thecoating process method according to claim 7, wherein the stop of thedischarging of the coating liquid is detected by using an opticalsensor.
 10. The coating process method according to claim 9, wherein theoptical sensor includes an optical fiber sensor for projecting light andan optical fiber sensor for receiving light.
 11. The coating processmethod according to claim 7, wherein the start of the discharging of thecoating liquid is detected by using a CCD camera.
 12. The coatingprocess method according to claim 7, wherein the start of thedischarging of the coating liquid is detected when the coating liquid isdischarged from the coating liquid discharging nozzle onto the targetsubstrate.
 13. The coating process method according to claim 7, whereinthe start of the discharging of the coating liquid is detected when thecoating liquid discharging nozzle discharges the coating liquid from aposition retreated from the target substrate.
 14. A coating processmethod in which a coating liquid is discharged onto the surface of atarget substrate to be processed while rotating the target substrate soas to expand the coating liquid radially outward on the target substrateand, thus, to form a coated film, comprising the steps of: detectingthat the actual discharging of a coating liquid from a coating liquiddischarging nozzle is stopped; and controlling based on a signal of thedetection at least one of the drive stop timing of a pump for allowingthe coating liquid to cease to be discharged from the coating liquiddischarging nozzle, the operation timing of a valve mounted to a pipefor supplying the coating liquid into the coating liquid dischargingnozzle, and the rotation stop timing of the target substrate.
 15. Thecoating process method according to claim 14, wherein, in thecontrolling step, a signal denoting that the discharging of the coatingliquid from the coating liquid discharging nozzle has been actuallystarted is obtained, and a delay time from the timing of actuallydischarging the coating liquid is obtained based on the detected signalso as to control based on the delay time at least one of the drive stoptiming of a pump for allowing the coating liquid to cease to bedischarged from the coating liquid discharging nozzle, the operationtiming of a valve mounted to a pipe for supplying the coating liquidinto the coating liquid discharging nozzle, and the rotation stop timingof the target substrate.
 16. The coating process method according toclaim 14, wherein the stop of the discharging of the coating liquid isdetected by using an optical sensor.
 17. The coating process methodaccording to claim 16, wherein the optical sensor includes an opticalfiber sensor for projecting light and an optical fiber sensor forreceiving light.
 18. The coating process method according to claim 14,wherein the stop of the discharging of the coating liquid is detected byusing a CCD camera.
 19. The coating process method according to claim14, wherein the stop of the discharging of the coating liquid isdetected when the coating liquid is discharged from the coating liquiddischarging nozzle onto the target substrate.
 20. The coating processmethod according to claim 14, wherein the stop of the discharging of thecoating liquid is detected when the coating liquid discharging nozzledischarges the coating liquid from a position retreated from the targetsubstrate.
 21. A coating process apparatus in which a coating liquid isdischarged onto the surface of a target substrate to be processed whilerotating the target substrate so as to expand the coating liquidradially outward on the target substrate and, thus, to form a coatedfilm, comprising: a substrate holding member for holding substantiallyhorizontal a target substrate to be processed; a motor for rotating thesubstrate holding member; a coating liquid discharging nozzle fordischarging a coating liquid onto the target substrate held by thesubstrate holding member; a pump for allowing the coating liquid to bedischarged from the coating liquid discharging nozzle; a valve mountedto a pipe for supplying the coating liquid into the coating liquiddischarging nozzle; a detecting device optically detecting that thedischarging of the coating liquid from the coating liquid dischargingnozzle has been started; and a controller receiving a signal of thedetection from the detecting device so as to control based on thedetection signal at least one of the drive timing of the pump forallowing the coating liquid to be discharged from the coating liquiddischarging nozzle, the operation timing of the valve, and the drivestarting or stopping timing of the motor.
 22. The coating processapparatus according to claim 21, wherein the controller obtains a delaytime from the timing of actually discharging the coating liquid based onthe signal detected by the detecting device and controls based on thedelay time at least one of the drive timing of the pump for allowing thecoating liquid to be discharged from the coating liquid dischargingnozzle, the operation timing of the valve and the drive starting orstopping timing of the motor.
 23. The coating process apparatusaccording to claim 21, wherein the detecting device includes an opticalsensor.
 24. The coating process apparatus according to claim 21, whereinthe optical sensor includes an optical fiber sensor for projecting lightand an optical fiber sensor for receiving light.
 25. The coating processapparatus according to claim 21, wherein the detecting device includes aCCD camera.
 26. The coating process apparatus according to claim 21,wherein the detecting device performs its detecting function when thecoating liquid is discharged from the coating liquid discharging nozzleonto the target substrate.
 27. The coating process apparatus accordingto claim 21, wherein the detecting device performs its detectingfunction when the coating liquid discharging nozzle discharges thecoating liquid from a position retreated from the target substrate. 28.A coating process apparatus in which a coating liquid is discharged ontothe surface of a target substrate to be processed while rotating thetarget substrate so as to expand the coating liquid radially outward onthe target substrate and, thus, to form a coated film, comprising: asubstrate holding member for holding substantially horizontal a targetsubstrate to be processed; a motor for rotating the substrate holdingmember; a coating liquid discharging nozzle for discharging a coatingliquid onto the target substrate held by the substrate holding member; apump for allowing the coating liquid to be discharged from the coatingliquid discharging nozzle; a valve mounted to a pipe for supplying thecoating liquid into the coating liquid discharging nozzle; a detectingdevice for optically detecting that the discharging of the coatingliquid from the coating liquid discharging nozzle has been finished; anda controller receiving a signal of the detection from the detectingdevice so as to control based on the detected signal at least one of thedrive stop timing of the pump for allowing the coating liquid to ceaseto be discharged from the coating liquid discharging nozzle, theoperation timing of the valve, and the stop timing of the motor.
 29. Thecoating process apparatus according to claim 28, wherein the controllerobtains a delay time from the timing of actually discharging the coatingliquid based on the signal detected by the detecting device and controlsbased on the delay time at least one of the drive stop timing of thepump for allowing the coating liquid to cease to be discharged from thecoating liquid discharging nozzle, the operation timing of the valve andthe drive starting or stop timing of the motor.
 30. The coating processapparatus according to claim 28, wherein the detecting device includesan optical sensor.
 31. The coating process apparatus according to claim30, wherein the optical sensor includes an optical fiber sensor forprojecting light and an optical fiber sensor for receiving light. 32.The coating process apparatus according to claim 28, wherein thedetecting device includes a CCD camera.
 33. The coating processapparatus according to claim 28, wherein the detecting device performsits detecting function when the coating liquid is discharged from thecoating liquid discharging nozzle onto the target substrate.
 34. Thecoating process apparatus according to claim 28, wherein the detectingdevice performs its detecting function when the coating liquiddischarging nozzle discharges the coating liquid from a positionretreated from the target substrate.
 35. A coating process method inwhich a coating liquid is discharged onto the surface of a targetsubstrate to be processed while rotating the target substrate so as toexpand the coating liquid radially outward on the target substrate and,thus, to form a coated film, comprising the steps of: actually detectingthe state in starting and/or stopping the discharging of the coatingliquid from a coating liquid discharging nozzle; and controlling basedon the data detected in the detecting step the operating speed of avalve mounted to a pipe for supplying the coating liquid into thecoating liquid discharging nozzle in a manner to permit the state instarting and/or stopping the discharging of the coating liquid to fallwithin an allowable range.
 36. A coating process method in which acoating liquid is discharged onto the surface of a target substrate tobe processed while rotating the target substrate so as to expand thecoating liquid radially outward on the target substrate and, thus, toform a coated film, comprising the steps of: detecting that the coatingliquid is being actually discharged from the coating liquid dischargingnozzle; measuring the actual discharging time during which thedischarging of the coating liquid was detected in the detecting step;comparing the actual discharging time measured in the measuring stepwith the set time for the discharging of the coating liquid; and judgingthat there is an abnormality in the case where the difference betweenthe actual discharging time and the set time is not smaller than anallowable value.
 37. A coating process apparatus, comprising: asubstrate holding member for holding substantially horizontal a targetsubstrate to be processed; a motor for rotating the substrate holdingmember; a coating liquid discharging nozzle for discharging a coatingliquid onto the target substrate held by the substrate holding member; apump for allowing the coating liquid to be discharged from the coatingliquid discharging nozzle; a valve mounted to a pipe for supplying thecoating liquid into the coating liquid discharging nozzle; a detectingdevice for optically detecting the state in starting and/or stopping thedischarging of the coating liquid from the coating liquid dischargingnozzle; and a controller for controlling based on the data detected bythe detecting device the operating speed of the valve in a manner topermit the state in starting and/or stopping the discharging of thecoating liquid to fall within an allowable range.
 38. A coating processapparatus, comprising: a substrate holding member for holdingsubstantially horizontal a target substrate to be processed; a motor forrotating the substrate holding member; a coating liquid dischargingnozzle for discharging a coating liquid onto the target substrate heldby the substrate holding member; a pump for allowing the coating liquidto be discharged from the coating liquid discharging nozzle; a valvemounted to a pipe for supplying the coating liquid into the coatingliquid discharging nozzle; a detecting device for optically detectingthat the coating liquid is being actually discharged from the coatingliquid discharging nozzle; a timer for measuring the actual dischargingtime during which the discharging of the coating liquid is detected bythe detecting device; a controller for comparing the actual dischargingtime measured by the timer with the set time of the coating liquiddischarging; and judging that there is an abnormality in the case wherethe difference between the actual discharging time and the set time isnot smaller than an allowable value.